1. Field
The present invention generally relates to ultrasound diagnostic systems, and more particularly to an ultrasound diagnostic system and a method for forming multiple receiving scan lines.
2. Background
An ultrasound diagnostic system has become an important and popular diagnostic tool since it has a wide range of applications. Specifically, due to its non-invasive and non-destructive nature, the ultrasound diagnostic system has been extensively used in the medical profession. The ultrasound is transmitted to a target object through a probe equipped in the ultrasound diagnostic system. Ultrasound echoes from the target object reach the probe. The ultrasound echoes are converted into electrical receiving signals in analog-form. Ultrasound images are formed based on the electrical receiving signals obtained from the ultrasound echoes.
A higher frame rate and increased ultrasound transmission events can guarantee excellent ultrasound images. However, the frame rate is inversely proportional to the number of ultrasound transmission events. Therefore, the ultrasound image must be prevented from degrading, even if the number of ultrasound transmittance events is decreased.
In order to increase the frame rate under the same number of ultrasound transmission events, there exists a method of forming multiple receiving scan lines from one original receiving scan line. In this method, ultrasound outputted from the probe is focused on one transmittance scan line, wherein multiple receiving scan lines are simultaneously formed with ultrasound echoes from the scan line. That is, the multiple scan lines are formed with the ultrasound echoes generated by one transmission event.
In a conventional ultrasound diagnostic system, digital receiving signals are formed by converting the analog receiving signals at a constant extraction rate. Further, a receiving scan line is formed with the digital receiving signals. A time divisional method is used to form multiple scan lines at one time, and all the multiple scan lines should be configured within the same time allowed for single scan line. For an example, one scan line of triple scan lines should be configured within ⅓ time allowed for the single scan line, and therefore the amount of the data is limited in proportional to the allowed time.
If the conventional diagnostic system is designed to extract data at 60 MHz for configuring the single scan line, as the number of receiving scan lines is increased from single to dual, triple or quadruple receiving scan line, the extraction rate per one scan line of the multiple scan lines must be reduced from 60 MHz to 30 MHz, 20 MHz or 15 MHz, respectively. This means that the extraction rate of the single receiving signal is unnecessarily high and the ultrasound diagnostic system should process lots of useless data due to over-sampling. Further, when designing the conventional ultrasound diagnostic system, the change in extraction rates must be considered, which causes an increase in the costs of manufacturing the system.